Question

State the difference between Schottky and Frenkel defects. Which of these two changes the density of the solid?

Answer 1

S. No.	Schottky defect	Frenkel defect
1.	It arises when an equal number of cations and anions are missing from their normal lattice sites.	It arises when ions (generally cations) leave their lattice sites and occupy interstitial sites between the lattice points.
2.	It is common in highly ionic compounds with high coordination numbers and having cations and anions of almost equal size.	It is common in those ionic compounds which possess a low coordination number and whose anions are much larger than the cations.
3.	It decreases the density of the crystal.	It does not affect the density of the crystal.
4.	It has no effect on the dielectric constant of the crystal.	It increases the dielectric constant of the crystal because similar charges come closer in this defect.
5.	Examples: NaCl, KCl, CsCl, AgBr	Examples: AgCl, AgBr, ZnS